Slip in 10 more piece types

Slip in 10 more piece types

Five new piece type without a defined image are added to increase the
length to the unpromoted series from 11 to 16. They all map behind
the Lion, which remains the 11th piece. Five promoted types are added
as well, just before King. No images are defined for these pieces (yet),
not even image-file names, so they can only be used with the 'Tile'
fallback and a user-defined inscription.